1. Field of the Invention
The present invention relates to an evaporator in which heat exchange units are arranged in parallel at the windward side and the leeward side.
2. Description of the Related Art
As disclosed in Japanese Patent Applications Laid-Open No. 6-74679, No. 10-238896 and No. 2000-105091, there has been conventionally proposed an evaporator in which heat exchange units are arranged in parallel at the windward side and the leeward side. FIG. 1 shows an example of this type of evaporator in which heat exchange units are arranged in parallel at the windward side and the leeward side. The evaporator 100 shown in FIG. 1 is configured so that a leeward heat exchange unit 110 comprised of an upper tank 111, a lower tank 112 and a plurality of heat exchange passages communicating the both tanks 111 and 112 and a windward heat exchange unit 120 comprised of an upper tank 121, a lower tank 122 and a plurality of heat exchange passages communicating the both tanks 121 and 122 are arranged so as to be superimposed in front and behind in the ventilating direction.
In leeward inlet heat exchange unit 110, an evaporator inlet 107 is provided at the right end of the upper tank 111, the upper tank 111 is divided into an upper first tank 111a and upper second tank 111b with a partition 114, the lower tank 112 is divided into a lower first tank 112a and a lower second tank 112b with a partition 1 15. Accordingly, the plurality of laminated heat exchange passages in multistage are divided into a first path 110a, a second path 110b and a third path 110c from right to left. A refrigerant introduced from the evaporator inlet 107 into the leeward heat exchange unit 110 flows from the upper first tank part 111a, the first path 110a, the lower first tank part 112a, the second path 110b, the upper second tank part 111b, the third path 110c to the lower second tank part 112b in this order. Then, the refrigerant is introduced from the lower second tank part 112b as a most downstream part of the leeward heat exchange unit 110 to the lower first tank part 122a as a most upstream part of the windward heat exchange unit 120 through a communicating path 109.
On the other hand, in the windward heat exchange unit 120, the lower tank 122 is divided into a lower first tank part 122a and a lower second tank part 122b with a partition 124, while the upper tank 121 is divided into an upper first tank part 121a and an upper second tank part 121b with a partition 125. The plurality of laminated heat exchange passages in multistage is divided into a first path 120a, a second path 120b and a third path 120c from left to right. The refrigerant introduced from communicating path 109 into the windward heat exchange unit 120 flows from the lower first tank part 122a, the first path 120a, the upper first tank part 121a, the second path 120b, the lower second tank part 122b, the third path 120c to the upper second tank part 121b in this order. Then, the refrigerant is derived from an evaporator output 108 provided at a right end of the upper second tank part 121b as a most downstream part of the windward heat exchange unit 120.
Each pair of paths which overlap one other at the windward side and the leeward side are superimposed to each other in the ventilating direction. In the pair of paths which overlap one another (110a and 120c), (110b and 120b), (110c and 120a), the refrigerant flows in a reverse direction to each other, including flow in the upstream and downstream tank parts. Circled numbers in the figure refer to the order by which the refrigerant flows in these paths.
FIG. 2A shows distribution of liquid refrigerant in each of the heat exchange units 110 and 120, and FIG. 2B shows distribution of the liquid refrigerant in whole of the evaporator in which the heat exchange units are superimposed. The distribution of the liquid refrigerant substantially corresponds to the distribution of temperature. As shown in FIG. 2B, in the evaporator 100 in which two heat exchange units are laminated in the air flow direction, since the two heat exchange units can be complemented in respect to heat exchange, variations in temperature distribution can be reduced, compared with an evaporator with one heat exchange unit.
However, variations in temperature distribution are essentially inevitable. The variations is due to that air cannot be cooled appropriately in the region where the liquid-phase refrigerant does not flow, that is, where only gas-phase refrigerant flows.